Occult dural arteriovenous fistula causing rapidly progressive conus medullaris syndrome and paraplegia after lumbar microdiscectomy

Abstract

A spinal dural arteriovenous fistula (DAVF) is a known cause of venous congestive myelopathy. These lesions are thought to be acquired. There exist two prior reports that describe DAVF presenting with slowly progressive myelopathy years after lumbar disc surgery. We report the first case of a preexistent, asymptomatic DAVF that became acutely symptomatic after lumbar microdiscectomy causing rapidly progressive conus medullaris syndrome and paraplegia. Case report. A 53-year-old Caucasian male presented with urinary retention, fecal incontinence, and progressive loss of function in bilateral lower extremities less than 3 months after a lumbar discectomy at an outside facility. The patient underwent microdiscectomy at L4/L5 and L5/S1 for left-sided radicular symptoms and evidence of herniated discs on magnetic resonance imaging (MRI). The patient's preoperative pain improved after the discectomy, but his bowel, bladder, and lower extremity function deteriorated steadily after discharge. Postoperative MRI showed salient serpentine vessels in the region of L1 and L2 with an enlarged T2 bright conus medullaris. Retrospective review of preoperative MRI revealed the presence of similar but less pronounced findings. A spinal arteriogram confirmed concerns of an arteriovenous malformation. The patient was transferred to our facility for definitive management of his DAVF via catheter embolization. Complete fistula obliteration was confirmed at the time of embolization and at 8 weeks follow-up with selective spinal angiography. The appearance of the conus medullaris normalized on follow-up MRI. The patient made a slow but significant recovery in rehabilitation. He regained the ability to independently ambulate but remains significantly disabled secondary to residual lower extremity weakness and spasticity. He continues self-catheterization for persistent neurogenic bladder dysfunction. This represents the first case of an occult spinal DAVF becoming acutely symptomatic after lumbar disc surgery. Although the etiology of the lesion and its symptomatic progression remains unknown, an alteration of blood flow through the DAVF as a result of surgery may have resulted in progressive venous congestive myelopathy. The present case highlights the importance of considering a spinal DAVF in the differential diagnosis of any patient with signs of myelopathy or conus medullaris syndrome after lumbar discectomy. In addition, this case underscores the gravity of recognizing subtle features that suggest the presence of an occult vascular malformation on preoperative imaging, as symptomatic progression of these lesions carries significant potential morbidity.